Heat exchanger

ABSTRACT

A method for making a heat exchanger includes providing a first outer tube, and an inner tube disposed in the first outer tube; placing a first coiled heat-transfer tube in a space defined between the inner tube and the first outer tube without being fixed to either one of an outer peripheral surface of the inner tube and an inner peripheral surface of the first outer tube, the first coiled heat-transfer tube including a plurality of coiled sections, an inside space of the heat-transfer tube defining a first flow path, a coiled space defined between coiled sections of the heat-transfer tube in the space, defined between the inner tube and the first outer tube, defining a second flow path, wherein heat is exchanged between two fluids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of co-pending U.S. patent applicationSer. No. 13/395,155 filed on Apr. 18, 2012, which is the National Phaseof PCT International Application No. PCT/JP2009/069815 filed on Nov. 24,2009, all of which are hereby expressly incorporated by reference intothe present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a heat exchanger. More specifically,the present invention relates to a heat exchanger such as a heater or acooler capable of performing low flow processing of a fluid to beprocessed, especially, for the use of chemical experiments.

Discussion of the Related Art

Examples of performance generally required for the heat exchangerinclude heat exchanging performance, corrosion resistance, pressuretightness, robustness, cleaning properties, and downsizing. The heatexchanger also requires low cost production thereof. A multipipe heatexchanger, a double-pipe heat exchanger, a coiled heat exchanger, aplate heat exchanger, and the like are mainly used as the conventionalheat exchanger. Such heat exchangers, however, have the complexstructures or have difficulties in downsizing, is costly, and lowcleaning properties. Especially, examples of the heat exchanger to beused in low flow processing, more specifically, in chemical experimentsgenerally include a glass coil type heat exchanger and a glassdouble-pipe heat exchanger. In this case, the good heat exchangingperformance is not expected because of low thermal conductivity of theglass itself. However, a large effort is required in cleaning theprocessed product adhering to a coil, or a perfect cleaning cannot berealized in some cases. As a result, many heat exchangers must beprepared, which is costly. Further, there is a high breakage risk. Morespecifically, in a case where a harmful processed product is passed,security measures therefore will also be costly.

As disclosed in Patent Document 1, conventionally known is a heatexchanger including a coiled heat-transfer tube placed in a spacedefined between an inner tube and an outer tube, wherein an inside spaceof the heat-transfer tube is used as one of flow paths, a coiled spacebetween coiled sections of the heat-transfer tube in the space is usedas the other flow path, and wherein an efficient heat exchange isachieved between one fluid and the other fluid.

However, in the heat exchanger disclosed in Patent Document 1, theheat-transfer tube is not fixed to either one of an outer peripheralsurface of the inner tube or an inner peripheral surface of the outertube but the heat-transfer tube is only naturally mounted. Therefore, ina case of a high-viscosity fluid, the heat-transfer tube expands orcontracts due to a flow resistance, which may cause, for example,pitches between coiled sections to be non-uniform and partially narroweror tighter.

In consideration of production and disassembly of the heat exchanger ofPatent Document 1, in a case of attachment and detachment of the coiledheat-transfer tube in the space defined between the inner tube and theouter tube, if a clearance between the heat-transfer tube, and the innertube and the outer tube is increased, the attachment and the detachmentof the coiled heat-transfer tube becomes easier. However, the coiledheat-transfer tube becomes freely movable in the space and thus aproblem due to the expansion and contraction of the heat-transfer tubemay arise. On the other hand, if the clearance is eliminated, theattachment and detachment of the heat-transfer tube will be difficult.

RELATED ART DOCUMENT Patent Document

Patent Document 1: JP2002-147976A

SUMMARY OF THE INVENTION

In view of the above, the present invention is to improve one type ofheat exchangers, which includes a coiled heat-transfer tube placed in aspace defined between an inner tube and an outer tube. An inside spaceof the heat-transfer tube is used as one of flow paths, and a coiledspace defined between coiled sections of the heat-transfer tube in thespace is used as the other flow path. Heat is exchanged between onefluid and the other fluid. More specifically, a purpose of the presentinvention is to provide a heat exchanger to/from which the heat-transfertube can be attached or detached with ease. Further, another purpose ofthe present invention is to provide a heat exchanger capable ofcontrolling a variation of the flow path area caused by a deformation ofthe heat-transfer tube due to a flow resistance. The present inventionis directed to provide the heat exchanger that can achieve either one ofthe above described purposes. A more specific purpose of the presentinvention is to provide a heat exchanger that is small, has a good heatexchange property, and can perform low flow processing in which a fluidto be processed can be passed, especially, in various chemicalexperiments, with a cost less than those of the conventional heatexchangers.

To solve the above problems, the invention recited in claim 1 provides aheat exchanger. The heat exchanger includes a coiled heat-transfer tube1 placed in a space 7 defined between an inner tube 5 and an outer tube6. An inside space of the heat-transfer tube 1 is used as one of flowpaths, and a coiled space 4 between coiled sections of the heat-transfertube 1 in the space 7 is used as the other flow path. Heat is exchangedbetween one fluid and the other fluid. The heat exchanger also includesa tensioning mechanism for keeping an expansion or contraction force forexpanding or contracting a diameter of the coiled heat-transfer tube 1than a diameter the heat-transfer tube 1 naturally has. The heat isexchanged between one fluid and the other fluid while the expansion andcontraction force is applied to the heat-transfer tube 1 by thetensioning mechanism.

The invention recited in claim 2 provides the heat exchanger of claim 1,wherein the heat-transfer tube 1 may not be fixed either one of an outerperipheral surface of the inner tube 5 or an inner peripheral surface ofthe outer tube 6, and the tensioning mechanism may expand or contract adiameter of the coiled heat-transfer tube 1 than a diameter the tubenaturally has, thereby bringing the heat-transfer tube 1 into closecontact with or pressure contact against the inner tube 5 or the outertube 6.

The invention recited in claim 3 provides the heat exchanger of claim 1or 2, wherein a load in a coil axis direction applied may be equal to orless than 10 kg when the heat-transfer tube 1 varies a length of thecoil in the coil axis direction by 10% in comparison with the length ofthe tube as it naturally has.

The invention recited in claim 4 provides the heat exchanger of claim 3,wherein the heat-transfer tube 1 may be made of a material selected fromthe group consisting of metals such as stainless steel, hastelloy,inconel, titanium, copper, and nickel; acrylic resins such as ABS,polyethylene, polypropylene, and PMMA; fluorine based resins such aspolycarbonate, PTFE, and PFA; and an epoxy resin.

The invention recited in claim 5 provides the heat exchanger of claim 4,wherein an outer diameter of the heat-transfer tube 1 is equal to orless than 28 mm.

The invention recited in claim 6 provides a heat exchanger. The heatexchanger includes a coiled heat-transfer tube 1 placed in a space 7defined between an inner tube 5 and an outer tube 6. An inside space ofthe heat-transfer tube 1 is used as one of flow paths, and a coiledspace 4 between coiled sections of the heat-transfer tube 1 in the space7 is used as the other flow path. Heat is exchanged between one fluidand the other fluid. In the heat exchanger, the coiled heat-transfertube 1 is elastically deformed from its natural state so as to bebrought into close contact with or pressure contact against the innertube 5 or the outer tube 6 and the heat is exchanged between one fluidand the other fluid while the heat-transfer tube 1 is elasticallydeformed.

The heat exchanger according to the present invention keeps a state thatthe expansion or contraction force is applied to the heat-transfer tube1 by the tensioning mechanism in use, i.e., at least during the heatexchange. Therefore, the heat-transfer tube always receives the forceand thus a deformation of the heat-transfer tube due to the flowresistance hardly occurs even if the heat-transfer tube does not contactthe inner tube 5 or the outer tube 6. Therefore, a non-uniformdeformation of the coiled heat-transfer tube 1 can be reduced. Moredesirably, even if the heat-transfer tube 1 is not fixed to either oneof the outer peripheral surface of the inner tube 5 and the innerperipheral surface of the outer tube 6, the deformation occurs less bybringing the heat-transfer tube 1 to close contact with or pressurecontact against the inner tube 5 or the outer tube 6 by an action of thetensioning mechanism.

Another operation and effect of the heat exchanger according to thepresent invention is to make the coiled heat-transfer tube 1 be easilyattached or detached. More specifically, the heat-transfer tube 1 isplaced freely with a suitable clearance defined between the inner tube 5and the outer tube 6. Then, the heat-transfer tube 1 is placed in atensed state to generate the expansion and contraction force to bebrought into contact with either one of the inner tube 5 or the outertube 6. The expansion and contraction force is then kept by thetensioning mechanism, thereby keeping the contacting state. Upondisassembly and the like, the expansion or contraction force is releasedto allow the heat-transfer tube to be detached with ease. Alternatively,the heat-transfer tube is placed in a pressure contact state by applyingthe expansion or contraction force after it is attached without theclearance (i.e., in the contacting state). Then, the pressure contactstate is kept by the tensioning mechanism. Upon disassembly, theexpansion or contraction force is released to allow the heat-transfertube to be detached relatively easier.

More specifically, in addition to an effective heat exchange, theheat-transfer tube can be replaced easily even when a clogging oradhesion occurs in the heat-transfer tube. Therefore, disposal of orexpensive cleaning the heat exchanger itself is no longer necessary asit is required in the conventional heat exchangers. Further, anoccurrence of the expansion or contraction of the heat-transfer tube dueto a flow of heating medium can be avoided. Still further, since thestructure can be simplified in comparison with the conventional ones,manufacturing steps can be reduced. As a result, the heat exchanger canbe provided with lower cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) illustrates a configuration of a heat exchanger according toone embodiment of the present invention and FIG. 1(B) is a plan viewthereof.

FIG. 2(A) illustrates a configuration of a heat exchanger according toanother embodiment of the present invention and FIG. 2(B) is a plan viewthereof.

FIG. 3(A) illustrates a configuration of a heat exchanger according tostill another embodiment of the present invention and FIG. 3(B) is aplan view thereof.

FIG. 4(A) is an enlarged view of a substantial portion of the heatexchanger according to the embodiment of the present invention inassembling and FIG. 4(B) is an enlarged view of a substantial portion ofthe heat exchanger when the assembling processing is completed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

One embodiment of the present invention is described below withreference to the accompanying drawings. The terms “up,” “down,” “left”and “right” as used herein only refers to relative positionalrelationships but do not specify absolute positions.

As illustrated in FIG. 1, a heat exchanger of this embodiment includesan inner tube 5 and an outer tube 6 which have a substantially circularlateral cross section, wherein upper ends and lower ends of the innertube 5 and the outer tube 6 are closed by an upper closing part 9 and alower closing part 8, respectively. In this example, the inner tube 5and the lower closing part 8 are integrally formed. According to anotherembodiment, not the lower closing part 8 but the upper closing part 9may be integrally formed with the inner tube 5. Alternatively, none ofthe lower closing part 8 or the upper closing part 9 is integrallyformed with the inner tube 5 but may be formed detachably.

A coiled heat-transfer tube 1 is placed in the space 7 defined betweenthe inner tube 5 and the outer tube 6 such that the coiled heat-transfertube 1 closely contacts with or pressure contacts against at leasteither one of an outer perimeter of the inner tube 5 or an innerperimeter of the outer tube 6. The coiled heat-transfer tube 1 piercesthrough the upper closing part 9 and the lower closing part 8, therebybeing contactable with pipes outside the heat exchanger. However, theheat-transfer tube 1 is not fixed to either one of the outer peripheralsurface of the inner tube 5 or the inner peripheral surface of the outertube 6. A coiled space 4 is defined between turns of the coiledheat-transfer tube 1. The coiled space 4 having predetermined intervalsis enclosed by the vertically adjacent different turns of theheat-transfer tube 1 and the inner and outer tubes 5, 6. The illustratedcoiled heat-transfer tube 1, inner tube 5 and outer tube 6 areimplemented in a cylindrical shape having a vertically uniform diameter.However, they may be formed into a shape having a vertically varyingdiameter (i.e., a circular truncated cone shape or an inverted circulartruncated cone shape).

A fluid 2 to be processed, e.g., water, an organic solvent, a solutionobtained by dissolving a solute, or a microparticle dispersion liquid,passes through an inside of the heat-transfer tube 1. A preferablematerial for the heat-transfer tube 1 can expand and contract and has ahigh corrosion and pressure resistance, and robustness against thetarget fluid to be processed through the heat-transfer tube. Examples ofthe material for the heat-transfer tube include a metal such asstainless steel, hastelloy, inconel, titanium, copper, and nickel; anacrylic resin such as ABS, polyethylene, polypropylene, and PMMA; afluorine based resin such as polycarbonate, PTFE, and PFA; and an epoxyresin.

The external section of the heat-transfer tube 1 as the coiled space 4(in other words, the coiled space 4 defined between the heat-transfertube 1 and the heat-transfer tube 1) is a space for passing a heatingmedium 3. The heating medium 3 enters and exists through nozzles 10formed in the upper closing part 9 and the lower closing part 8,respectively. Accordingly, the heating medium 3 can be passed throughthe space 7 and the coiled space 4. To efficiently and effectivelyexchange heat of the fluid 2 to be processed, the fluid 2 to beprocessed is passed upwardly (i.e., in a U direction) in FIG. 1 and theheating medium 3 is passed downwardly (i.e., in an S direction) tocreate an absolute counterflow. Accordingly, both of the fluid 2 to beprocessed and the heating medium 3 are prevented from an increase of apressure loss, resulting in securing a large overall heat-transfercoefficient. However, a flow of both fluids in the same direction shouldnot be excluded from consideration.

Assembly and disassembly of the heat exchanger according to the presentinvention are described below. Initially, the heat-transfer tube 1 isassembled with the lower closing part 8 and the inner tube 5 which areintegrally formed. The above attachment can be performed smoothly bydefining a suitable clearance 4 c between the inner tube 5 and theheat-transfer tube 1 (See FIG. 4(A)). After the attachment, theheat-transfer tube 1 is fixed to the lower closing part 8. The fixationis performed with what having a tensioning mechanism 11. The tensioningmechanism 11 keeps the expansion or contraction force for expanding orcontracting the diameter of the coiled heat-transfer tube 1 than thediameter the coiled heat-transfer tube 1 naturally has. In theillustrated example, an interlocking joint 11 is employed as thetensioning mechanism 11. In another embodiment, the tensioning mechanismmay include a clamp, a saddle band, a strap, and a bracket. In addition,the tensioning mechanism may be a fixation by, for example, welding orbonding (not illustrated). The tensioning mechanism 11 may be configuredonly to keep the expansion or contraction force, whereas, generation ofthe expansion or contraction force may be performed by anothermechanism. However, in a case of the interlocking joint 11, it generatesas well as keeps the expansion or contraction force.

Then, the heat-transfer tube 1 is pulled in the U direction to reducethe diameter of the coiled heat-transfer tube 1, thereby bringing theheat-transfer tube 1 into close contact with or pressure contact againstthe inner tube 5 (FIG. 4(B)). Thereafter, the outer tube 6 slightlyspaced by a gap 4 d from the outer diameter of the assembled coiledheat-transfer tube 1, and the upper closing part 9 are assembledtherewith. The outer tube 6 and the upper closing part 9 may beintegrally formed or may be formed so as to be disassembled.

More specifically, the slight gap 4 d is kept while the heat-transfertube 1 is pulled in the U direction. The outer tube 6 is then mounted tothe outside of the heat-transfer tube 1 and the upper closing part 9 istemporally attached thereto. During the temporal attachment, while theheat-transfer tube 1 is still pulled in the U direction, an upper end ofthe heat-transfer tube 1 is fixed to the upper closing part 9, therebycompleting the attachment between the outer tube 6 and the upper closingpart 9. The tensioning mechanism 11 of the upper closing part 9 may beconfigured to be adjustable of an upper end position of the outer tube 6in the same manner as the interlocking joint 11 of the lower closingpart 8 or may be an unadjustable fixing mechanism.

At the time, for enabling an easy assembling and disassembling, when thecoiled heat-transfer tube 1 that can be expanded or contracted is variedby 10% of the expansion or contraction amount with respect to a lengththe coiled heat-transfer tube 1 naturally has, the load is preferablyequal to or less than 10 kg. Also, for the purpose of the low flowprocessing, for example, in various chemical experiments, the outerdiameter of the heat-transfer tube 1 is preferably equal to or less than28 mm. Thereby, the coiled heat-transfer tube 1 having a smaller coildiameter can be produced and thus the heat exchanger of a smaller sizecan be provided.

The above example is suitable for the heat-transfer tube 1 naturallyhaving an inner diameter larger than the outer diameter of the innertube 5. However, in a case where the inner diameter the heat-transfertube 1 naturally has is larger than the outer diameter of the inner tube5 and the outer diameter the heat-transfer tube 1 naturally has islarger than the inner diameter of the outer tube 6, the following methodis employable. During the above described temporal attachment, thetensile force in the U direction is released. Accordingly, the coiledheat-transfer tube 1 attempts to resume its natural size. As a result,the coiled heat-transfer tube 1 is brought into close contact with orpressure contact against the inner peripheral surface of the mountedouter tube 6. In that state where the heat-transfer tube close contactswith or pressure contacts against the outer tube 6, the upper end of theheat-transfer tube 1 is fixed to the upper closing part 9 to completethe attachment between the outer tube 6 and the upper closing part 9.

Alternatively, in a case where the inner diameter of the heat-transfertube 1 it naturally has is larger than the outer diameter of the innertube 5 and the outer diameter of the heat-transfer tube 1 it naturallyhas is smaller than the inner diameter of the outer tube 6, thefollowing method is also employable. In other words, the heat-transfertube 1 is attached with a suitable clearance 4 c between the inner tube5 and the heat-transfer tube 1, and the outer tube 6 having a slight gapwith the outer coil diameter of the heat-transfer tube 1 is assembledwith the upper closing part 9. In this state, the heat-transfer tube 1is pulled in the vertical direction so that the upper end and the lowerend thereof separate from each other by, for example, operating theinterlocking joint 11 to generate the expansion or contraction force(i.e., a contraction force in this case). Thereby, the diameter of thecoiled heat-transfer tube 1 is reduced to bring the heat-transfer tube 1into close contact with or pressure contact against the inner tube 5.The expansion or contraction force is then kept to secure the closecontact or pressure contact state.

In the above embodiment, the heat-transfer tube 1 is brought into closecontact with or pressure contact against the inner tube 5. However, inanother embodiment, the heat-transfer tube 1 is pushed downwardly intothe outer tube 6 from above, i.e., in the S direction (in other words,the upper end is brought closer to the lower end) to increase the coileddiameter, thereby bringing the heat-transfer tube 1 into close contactwith or pressure contact against the outer tube 6. Further, in the aboveexample, the upper end and the lower end of the heat-transfer tube 1 ispushed or pulled in the coil axial direction. However, the upper end andthe lower end of the heat-transfer tube 1 may be pushed or pulled in adirection in which a helical structure of the coil extends. The pushingor pulling direction can be changed, as required, provided that theexpansion or contraction force can be generated. In the abovedescription, the vertical orientation is exemplified, but theorientation may be inverted. More specifically, up and down can beinterpreted as one side and the other side, respectively.

According to the above invention, the heat-transfer tube 1 can be placedin the space 7 defined between the inner tube 5 and the outer tube 6 soas to be on a concentric circle of the inner and the outer tubes.Therefore, the coiled space 4 sandwiched between the adjacent coiledsections of the heat-transfer tube 1 in the space 7 can be used as aflow path of the heating medium 3. The heat exchanger according to thepresent invention can be disassembled with ease according to a reversedprocedure of the above assembling method.

In the case where the coiled heat-transfer tube 1 is not fixed in thespace 7, the heat-transfer tube 1 may expand or contract due to the flowresistance of the heating medium 3, which may invite a case that thepitches between the coiled sections of the heat-transfer tube 1 becometight. In other words, the flow resistance of the heating medium 3causes the coiled sections of the heat-transfer tube 1 become closer toeach other and finally the coiled heat-transfer tube 1 may move to adirection the coiled space 4 is eliminated. In this case, since theheating medium 3 becomes not to pass smoothly in the coiled space 4,there arises a problem that the heat exchange cannot work at all, thatthe effective/efficient heat exchange cannot be performed, or thatbreakage or short-life of the heat-transfer tube 1 may be induced. Inthe present invention, although the heat-transfer tube 1 is not fixed,the heat-transfer tube 1 close contacts with or pressure contactsagainst at least either one of the outer perimeter of the inner tube 5or the inner perimeter of the outer tube 6. Therefore, the coiledheat-transfer tube 1 can be prevented from the displacement caused dueto the flow resistance that is generated by the flow of the heatingmedium 3. As a result, the above described problems can be solved.

The heat-transfer tube 1 may include a plurality of heat-transfer tubes.The number of the heat-transfer tubes 1 to be assembled together is notparticularly limited. The number is determined according to a necessaryflow rate of the fluid to be processed or the number of types of fluidsto be treated. Examples of assembling the plurality of heat-transfertubes are illustrated with reference to FIGS. 2(A) and 2(B), and FIGS.3(A) and 3(B). For example, as illustrated in FIG. 2, in a case ofassembling the heat-transfer tubes 1 having the same coiled diameter,the heat-transfer tube 1 a and the heat-transfer tube 1 b are assembledwith the lower closing part 8 (or the upper closing part 9) and theinner tube 5, which are integrally formed, and are fixed at differentpositions on the lower closing part 8. Then, the heat-transfer tube 1 aand the heat-transfer tube 1 b are brought into close contact with orpressure contact against the inner tube 5 by the above describedmechanism, followed by being further assembled with the outer tube 6 andthe upper closing part 9 (or the lower closing part 8). Accordingly, theplurality of heat-transfer tubes 1 can be assembled. In anotherembodiment, as illustrated in FIG. 3, the coiled heat-transfer tubes 1may be implemented in a manner that the diameters of the coiledheat-transfer tubes are located on concentric circles. In this case, theheat-transfer tube 1 a is assembled with the lower closing part 8 (orthe upper closing part 9) and the inner tube 5 which are integrallyformed. The heat-transfer tube 1 a is then brought into close contactwith or pressure contact against the inner tube 5 by the above describedmechanism. Then, the outer tube 6 a spaced from the outer diameter ofthe coiled heat-transfer tube 1 a by the slight gap is assembledtherewith. Subsequently, the heat-transfer tube 1 b is assembled withthe lower closing part 8 (or the upper closing part 9) to bring theheat-transfer tube 1 b into close contact with or pressure contactagainst the outer peripheral surface of the outer tube 6 a by the abovedescribed mechanism. Then, the outer tube 6 b and the upper closing part9 (or the lower closing part 8) are assembled therewith. Accordingly,the plurality of heat-transfer tubes 1 can be assembled. In theembodiment illustrated in FIG. 3, the coiled spaces 4 a and 4 b aredefined. Even in a case where more than three heat-transfer tubes areassembled together, this configuration can be implemented using amaterial and an assembling method similar to those described above. Inthis case, the assembly can be performed by a combination of theassembly based on the same diameter and the assembly based on theconcentric circles.

As described above, passed through the heat-transfer tube 1 is the fluid2 to be processed such as water, organic solvent, solution that isproduced by dissolving solute, and microparticle dispersion liquid to beused in the low flow processing, more specifically, used in variouschemical experiments. Therefore, the heat-transfer tube 1 often needs tobe replaced depending on experiment descriptions. Furthermore, in a casewhere solid and powder contained in the fluid 2 to be processed, orsolute dissolved in the fluid 2 to be processed is precipitated due to achange of temperature or concentration or due to drying, such solidmatters may adhere or clog inside the heat-transfer tube 1 to invite anecessity of replacement of the heat-transfer tube 1.

In a submerged heat exchanger or double-pipe heat exchanger which isused in the typical low flow processing, especially, in various chemicalexperiments, a good efficiency in heat exchange cannot be expected.Therefore, the structure of the heat exchanger according to the presentinvention solves the above problems of the submerged heat exchanger andthe double-pipe heat exchanger. Further, as described above, in a casewhen the heat-transfer tube 1 is required to be replaced, the heatexchanger according to the present invention is characterized in that itcan be assembled or disassembled very easily because the heat exchangeraccording to the present invention has a very simple structure incomparison with the multipipe heat exchanger and the plate type heatexchanger. Also, in addition to the easy replacement of theheat-transfer tube, the heat exchanger can be easily disassembled andcleaned, so that it is not necessary to dispose the heat exchangeritself or perform a costly cleaning of the heat exchanger as it is donein the conventional heat exchanger.

There are a plurality of modes for achieving the close contact with orthe pressure contact against the inner tube 5 and the outer tube 6 byusing the elastic deformation of the heat-transfer tube. Such modes aredescribed below.

First Mode

It is provided that the outer diameter of the inner tube 5 is α, theinner diameter of the outer tube 6 is β, the inner diameter of thecoiled heat-transfer tube 1 is γ, and the outer diameter of the coiledheat-transfer tube 1 is θ. If the inner diameter γ of the coiledheat-transfer tube 1 is larger than or equal to the outer diameter α ofthe inner tube 5 (α □ γ), when the inner tube 5 is inserted into theheat-transfer tube 1 leaving it in the natural state and, theheat-transfer tube 1 is pulled in a direction in which both endsseparates from each other after the insertion, the outer diameter α ofthe inner tube 5 comes to be equal to the inner diameter γ of theheat-transfer tube 1 by the external force to bring the heat-transfertube 1 into close contact with or pressure contact against the innertube 5. Here, even in a case of α □ γ, the inner diameter γ may beincreased by compressing the heat-transfer tube 1 in order to facilitatethe insertion.

Second Mode

If the inner diameter γ of the coiled heat-transfer tube 1 is smallerthan the outer diameter α of the inner tube 5 (α>γ), the inner tube 5 isinserted while the heat-transfer tube 1 is compressed to expand theinner diameter γ. After the insertion, when the compressing force isreleased and the heat-transfer tube 1 is then pulled, as required, theouter diameter α of the inner tube 5 becomes equal to the inner diameterγ of the heat-transfer tube 1 due to the elastic deformation of theheat-transfer tube 1, thereby bringing the heat-transfer tube 1 intoclose contact with or pressure contact against the inner tube 5.

Third Mode

If the outer diameter θ of the coiled heat-transfer tube 1 is smallerthan or equal to the inner diameter β of the outer tube 6 (β≥θ), theheat-transfer tube 1 in its natural state is inserted into the outertube 6 and, the heat-transfer tube 1 is then compressed after theinsertion, the inner diameter β of the outer tube 6 comes to be equal tothe outer diameter θ of the heat-transfer tube 1 by the external force,thereby bringing the heat-transfer tube 1 into close contact with orpressure contact against the outer tube 6. Even in a case of β≥θ, theheat-transfer tube 1 may be pulled to reduce the outer diameter θthereof in order to facilitate the insertion.

Fourth Example

If the outer diameter θ of the coiled heat-transfer tube 1 is largerthan the inner diameter β of the outer tube 6 (β<θ), the heat-transfertube 1 is pulled to reduce the diameter thereof, and then inserted intothe outer tube 6. After the insertion, when the pulling force isreleased and the heat-transfer tube 1 is then compressed, as required,the inner diameter β of the outer tube 6 comes to be equal to the outerdiameter θ of the heat-transfer tube 1, thereby bringing theheat-transfer tube 1 into close contact with or pressure contact againstthe outer tube 6.

TABLE 1 Relation between Close- diameters contacting before State ofheat-transfer External force after component insertion tube 1 duringinsertion insertion Inner tube 5 α ≤ γ Natural state or Pulling forcecompressed state Inner tube 5 α > γ Compressed state Unnecessary orPulling force Outer tube 6 β ≥ θ Natural state or pulled Compressingforce state Outer tube 6 β < θ pulled state Unnecessary or Compressingforce

DESCRIPTION OF REFERENCE NUMERALS

-   -   1: Heat-Transfer Tube    -   3: Heating Medium    -   4: Coiled Space    -   5: Inner Tube    -   6: Outer Tube    -   8: Lower Closing Part    -   9: Upper Closing Part    -   11: Tensioning Mechanism

What is claimed is:
 1. A method for making a heat exchanger comprisingthe steps of: providing a first outer tube, and an inner tube disposedin the first outer tube; placing a first coiled heat-transfer tube in aspace defined between the inner tube and the first outer tube withoutbeing fixed to either one of an outer peripheral surface of the innertube and an inner peripheral surface of the first outer tube, the firstcoiled heat-transfer tube including a plurality of coiled sections, aninside space of the heat-transfer tube defining a first flow path for afirst fluid, a coiled space defined between coiled sections of theheat-transfer tube in the space, defined between the inner tube and thefirst outer tube, defining a second flow path for a second fluid,wherein heat is exchanged between the first and second fluids; exertingan expansion force on the first coiled heat-transfer tube to increase adiameter of the coiled sections of the first coiled heat-transfer tubeso as to be larger than the diameter the coiled sections of the firstcoiled heat-transfer tube naturally have, or a contraction force on thefirst coiled heat-transfer tube to decrease the diameter of the coiledsections of the first coiled heat-transfer tube so as to be smaller thanthe diameter the coiled sections of the first coiled heat-transfer tubenaturally have; connecting a first tensioning joint to the first coiledheat-transfer tube, and maintaining a state in which the expansion forceor the contraction force is applied to the first coiled heat-transfertube by the first tensioning joint, such that the first coiledheat-transfer tube is subjected to the expansion force, abuttingagainst, with a pressure, the inner peripheral surface of the firstouter tube without contacting the outer peripheral surface of the innertube, or subjected to the contraction force, abutting against, with apressure, the outer peripheral surface of the inner tube withoutcontacting the inner peripheral surface of the first outer tube, by anaction of the first tensioning joint even when the first coiledheat-transfer tube is not fixed either to the inner peripheral surfaceof the first outer tube or the outer peripheral surface of the innertube, wherein the heat exchange is performed between the first andsecond fluids in the state in which the expansion force or thecontraction force is applied to the first coiled heat-transfer tube bythe first tensioning joint.
 2. The method according to claim 1, whereinthe step of exerting comprises exerting the contraction force on thefirst coiled heat-transfer tube by fixating a first end of the firstcoiled heat-transfer tube and pulling a second end of the first coiledheat-transfer tube in a direction away from the first end of the firstcoiled heat-transfer tube before the second end of the first coiledheat-transfer tube is fixated by the first tensioning joint, or exertingthe expansion force on the first coiled heat-transfer tube by fixatingthe first end of the first coiled heat-transfer tube and pushing thesecond end of the first coiled heat-transfer tube in a direction towardthe first end of the first coiled heat-transfer tube before the secondend of the first coiled heat-transfer tube is fixated by the firsttensioning joint.
 3. The method according to claim 1, wherein the firstcoiled heat-transfer tube is configured in such a manner that when aload equal to or less than 10 kg is applied in a coil longitudinal axisdirection of the coiled heat-transfer tube, a length of the first coiledheat-transfer tube in the longitudinal coil axis direction is varied by10% in comparison with the length of the first coiled heat-transfer tubewhen no load being applied therein.
 4. The method according to claim 1,wherein the first coiled heat-transfer tube is made of at least amaterial selected from the group consisting of metals; acrylic resins;fluorine based resins; and an epoxy resin.
 5. The method according toclaim 4, wherein said metals are stainless steel, metal alloy, titanium,copper, or nickel; said acrylic resins are ABS, polyethylene,polypropylene or PMMA; and said fluorine based resins are polycarbonate,PTFE or PFA.
 6. The method according to claim 1, wherein an outerdiameter of the first coiled heat-transfer tube itself is equal to orless than 28 mm.
 7. The method according to claim 1, wherein the heatexchanger further comprises an upper closing part and a lower closingpart, the upper closing part closing the inner tube and the first outertube at an upper side, the lower closing part closing the inner tube andthe first outer tube at a lower side.
 8. The method according to claim7, further comprising the steps of: fixing the first coiledheat-transfer tube to the upper closing part at an upper fixing pointvia an upper part of the first tensioning joint; and fixing the firstcoiled heat-transfer tube to the lower closing part at a lower fixingpoint via a lower part of the first tensioning joint, wherein the firstcoiled heat-transfer tube is fixed to the upper and lower closing partsin a manner such that the coiled sections of the first coiledheat-transfer tube between the upper fixing point and the lower fixingpoint have the diameter larger than or smaller than the diameter thecoiled sections of the first coiled heat-transfer tube naturally have.9. The method according to claim 1, further comprising the steps of:providing a second outer tube outside of the first outer tube; placing asecond coiled heat-transfer tube in a space defined between the firstouter tube and the second outer tube without being fixed to either oneof the outer peripheral surface of the first outer tube and an innerperipheral surface of the second outer tube, the second coiledheat-transfer tube including a plurality of coiled sections, anddefining a third flow path for a third fluid, wherein heat is exchangedbetween the second and third fluids; exerting an expansion force on thesecond coiled heat-transfer tube to increase a diameter of the coiledsections of the second coiled heat-transfer tube so as to be larger thanthe diameter the coiled sections of the second coiled heat-transfer tubenaturally have, or a contraction force on the second coiledheat-transfer tube to decrease the diameter of the coiled sections ofthe second coiled heat-transfer tube so as to be smaller than thediameter the coiled sections of the second coiled heat-transfer tubenaturally have; and connecting a second tensioning joint to the secondcoiled heat-transfer tube, and maintaining a state in which theexpansion force or the contraction force is applied to the second coiledheat-transfer tube by the second tensioning joint, such that the secondcoiled heat-transfer tube is subjected to the expansion force, abuttingagainst, with a pressure, the inner peripheral surface of the secondouter tube without contacting the outer peripheral surface of the firstouter tube, or subjected to the contraction force, abutting against,with a pressure, the outer peripheral surface of the first outer tubewithout contacting the inner peripheral surface of the second outertube, by an action of the second tensioning joint even when the secondcoiled heat-transfer tube is not fixed either to the inner peripheralsurface of the second outer tube or the outer peripheral surface of thefirst outer tube, wherein coiled diameters of the first coiledheat-transfer tubes and the second coiled heat-transfer tube areconcentric, and wherein the heat exchange is performed between thesecond and third fluids in the state in which the expansion force or thecontraction force is applied to the first coiled heat-transfer tube bythe first tensioning joint, and in the state in which the expansionforce or the contraction force is applied to the second coiledheat-transfer tube by the second tensioning joint.
 10. The methodaccording to claim 9, wherein the step of exerting comprises exertingthe contraction force on the second coiled heat-transfer tube byfixating a first end of the second coiled heat-transfer tube and pullinga second end of the second coiled heat-transfer tube in a direction awayfrom the first end of the second coiled heat-transfer tube before thesecond end of the second coiled heat-transfer tube is fixated by thesecond tensioning joint, or exerting the expansion force on the secondcoiled heat-transfer tube by fixating the first end of the second coiledheat-transfer tube and pushing the second end of the second coiledheat-transfer tube in a direction toward the first end of the secondcoiled heat-transfer tube before the second end of the second coiledheat-transfer tube is fixated by the second tensioning joint.
 11. Themethod according to claim 9, wherein the heat exchanger furthercomprises an upper closing part and a lower closing part, the upperclosing part closing the inner tube and the second outer tube at anupper side, the lower closing part closing the inner tube and the secondouter tube at a lower side.
 12. The method according to claim 11,further comprising the steps of: fixing the first and second coiledheat-transfer tubes to the upper closing part at different upper fixingpoints via the upper part of the first tensioning joint and an upperpart of the second tensioning joint, respectively; and fixing the firstand second coiled heat-transfer tubes to the lower closing part atdifferent lower fixing points via the lower part of the first tensioningjoint and a lower part of the second tensioning join, respectively,wherein the first coiled heat-transfer tube is fixed to the upper andlower closing parts in a manner such that the coiled sections of thefirst coiled heat-transfer tube between the upper fixing points and thelower fixing points have the diameter larger than or smaller than thediameter the coiled sections of the first coiled heat-transfer tubenaturally have, and the second coiled heat-transfer tube is fixed to theupper and lower closing parts in a manner such that the coiled sectionsof the second coiled heat-transfer tube between the upper fixing pointsand the lower fixing points have the diameter larger than or smallerthan the diameter the coiled sections of the second coiled heat-transfertube naturally have, and wherein the diameter of the coiled sections ofthe first coiled heat-transfer tube between the upper fixing points andlower fixing points is smaller than the diameter of the coiled sectionsof the second coiled heat-transfer tube between the upper fixing pointsand lower fixing points.